As a disk recording medium device in which a disk-like recording medium capable of recording and/or reproducing information such as audio data, video data or computer data is accommodated within a cartridge housing so as to become freely rotatable, there is known a disk recording medium device having an arrangement shown in FIG. 42, for example. This disk recording medium device 1 is an information recording media which incorporates therein a write once magneto-optical disk on which users are able to record (write) information such as computer data later on.
This disk recording medium device 1 comprises a cartridge housing 2 composed of a pair of upper shell 2a and lower shell 2b, a magneto-optical disk 4 accommodated within a disk compartment 3 of this cartridge housing 2 so as to become freely rotatable and so forth. The cartridge housing 2 has on its upper and lower surfaces provided an upper and lower opening portion 5 that extends from a central portion to one side. This opening portion 5 can be opened and closed by a shutter member 6 that can slide along one side. The shutter member 6 is constantly spring-biased in the direction to close the opening portion 5 under spring force of a spring, not shown. Reference numeral 6a denotes a presser member for preventing a tip end portion of the shutter member 6 from being disengaged from the opening portion inadvertently.
The magneto-optical disk 4 has at its central portion provided a disk-like center hub 7 made of metal. This center hub 7 is located at the position opposing to the inner end portion of the opening portion 5, i.e. located at substantially the central portion of the cartridge housing 2. A turntable provided on the main body side of an information recording and reproducing apparatus is mounted to the center hub 7. The magneto-optical disk 4 is chucked to the turntable and thereby the magneto-optical disk is rotated at a predetermined velocity (e.g. constant linear velocity). At that time, a magneto-optical pickup device of which the head portion is inserted into the opening portion 5 functions to record or reproduce information on or from the magneto-optical disk 4.
However, in the conventional disk recording medium device having the above-mentioned arrangement, the shutter member 6 that is provided on the cartridge housing 2 so as to become freely slidable is constantly spring-biased in the direction in which it closes the opening portion 3 by a spring. When the disk recording medium device is in use, the shutter member 6 is slid in the direction in which it opens the opening portion 3 to open the opening portion against spring-biasing force of this spring. To this end, a disk recording and reproducing apparatus that records and reproduces an information signal by using this disk recording medium device 1 needs an open and hold mechanism for holding the shutter member 6 at the opening position in order to hold the opening portion 3 in the opened state while the disk recording medium device is in use.
While such open and hold mechanism is generally provided on the disk recording and reproducing apparatus, various vibration sources are existing on the disk recording and reproducing apparatus and shocks are applied to the disk recording and reproducing apparatus from the outside unavoidably. Vibrations generated from this disk recording and reproducing apparatus or shocks inputted to the disk recording and reproducing apparatus from the outside are transmitted through the open and hold mechanism to the disk recording medium device 1. As a result, when vibrations from the disk recording and reproducing apparatus are applied to the disk recording medium device 1, vibrations are transmitted to the magneto-optical disk 4 and a magneto-optical head of a magneto-optical pickup device and the like. There arises a problem in which an information signal is read out from and written in the magneto-optical disk 1 inaccurately.
When external shocks are applied to the disk recording medium device 1, it is unavoidable that the open and hold mechanism for holding the shutter member 6 at the opening position is disengaged from the disk recording and reproducing apparatus. In such case, the shutter member 6 that intends to move toward the closing direction is brought in contact with the optical head of the optical pickup device and the turntable. As a result, there is a risk that the optical head will be broken or that the shutter member 6 itself will be broken.
In particular, as a storage capacity of an optical disk is increasing progressively and a recording density is increasing progressively, pitches of recording patterns is becoming narrower and linear density is increasing more in recent years. Thus, when an information recording surface of a magnetic recording medium such as an optical disk and a magneto-optical disk is vibrated or smudged by dusts and the like, such vibrations and the smudged information recording surface hinder the optical pickup device from reading or writing information correctly. So that information cannot be read out from and written in the disk recording medium device normally.
In view of the aforesaid aspect, it is an object of the present invention to provide a disk cartridge, a disk recording medium device and a disk recording and/or reproducing apparatus in which when a shutter member has finished opening the opening portion, pressure from an open and hold mechanism of an external apparatus and which is used to hold the shutter member at the opening position can be prevented from being applied to a cartridge housing so that the shutter member can be held at the opening position by an inside mechanism.